Along with a recent trend of a high density and a high miniaturization of semiconductor devices, a plasma processing apparatus is used for performing a film forming process, an etching process, an ashing process and the like in a manufacturing process of the semiconductor devices. Especially, since a plasma can be stably generated in an environment at a high vacuum level in which a pressure is comparatively low, e.g., ranging from 0.1 to several tens mTorr, a plasma processing apparatus for processing a wafer by using a high-density plasma generated by a microwave tends to be used.
Such plasma processing apparatus is disclosed in Japanese Patent Laid-Open Publication Nos. 3-191073 and 5-343334 or Japanese Patent Laid-Open Publication No. 9-181052 filed by the applicant of the present invention. Herein, a conventional plasma processing apparatus using a microwave will be schematically described with reference to FIG. 9. FIG. 9 shows a view illustrating a conventional typical plasma processing apparatus.
Referring to FIG. 9, there is illustrated a plasma processing apparatus 2 having a workpiece mount base 6 for mounting thereon a semiconductor wafer W in an evacuatable processing vessel 4. Further, hermetically provided on a ceiling portion facing the workpiece mount base 6 is a microwave transmitting window 8, made of, e.g., disc-shaped aluminum nitride and the like, for transmitting a microwave. Specifically, the microwave transmitting window 8 is hermetically installed via a sealing member 14 such as an O-ring and the like on a supporting bracket 12 protruded inwardly along a radial direction of a ring-shaped supporting frame member 10, wherein the supporting frame member 10 made of, e.g., aluminum, is installed at an upper portion of the processing vessel 4.
Further, provided on a top surface of the microwave transmitting window 8 are a disc-shaped planar antenna member 16 having a thickness of several mm and a wave-delay member 18, if necessary, made of, e.g., a dielectric material, for shortening a wavelength of the microwave along a radial direction of the planar antenna member 16. A shield lid 19 made of a conductor is used for covering top portions of the planar antenna member 16 and the wave-delay member 18 and blocking a top portion of the processing vessel 4. Moreover, installed above the wave-delay member 18 is a ceiling cooling jacket 22 having therein a cooling water path 20 for allowing cooling water to flow therethrough to cool the shield lid 19 and the like. Besides, formed through the antenna member 16 are microwave radiation holes 24 including a plurality of approximately circular or slit-shaped through-holes. Additionally, an internal conductor 28 of a coaxial waveguide 26 is connected to a central portion of the planar antenna member 16. The coaxial waveguide 26 is connected to a rectangular waveguide 32 via a mode converter 30, and the rectangular waveguide 32 is sequentially connected to a matching circuit 34 and a microwave generating source 36. Accordingly, a microwave of, e.g., 2.45 GHz, generated from the microwave generating source 36 can be guided to the antenna member 16. The microwave which propagates along a radial direction of the antenna member 16 is emitted through the microwave radiation holes 24 provided in the antenna member 16 toward the microwave transmitting window 8. Then, the microwave transmitted through the microwave transmitting window 8 is introduced into the processing vessel 4, thereby generating a plasma in the processing vessel 4 to perform a plasma processing such as an etching, a film formation and the like on a semiconductor wafer W.
The microwave generating source 36 described above typically generates a high power of about 5 KW and, therefore, the matching circuit 34 for restricting a reflection wave to be generated becomes large. Accordingly, the matching circuit 34 is provided on a floor portion which is located at an outside of a frame of the plasma processing apparatus 2 so that a relatively long rectangular waveguide 32 must be used to connect the matching circuit 34 to the mode converter 30.
Maintenance and repairing works of such plasma processing apparatus 2 are regularly or irregularly carried out. At this time, the shield lid 19 or the microwave transmitting window 8 is separated to examine the antenna member 16, the wave-delay member 18, a structure in the processing vessel 4 and the like.
However, in order to separate the shield lid 19 covering the top portion of the processing vessel 4, the long and large rectangular waveguide 32 connected to the shield lid 19 as one body should be separated by loosening screws and the like (not shown) of a flange portion 32A. Thus, the maintenance and the repairing works of the plasma processing apparatus 2 become quite complex.
Further, as described above, since a length of the rectangular waveguide 32 is relatively long, a multiple reflection of the microwave can easily occur therein and further, a load will be increased accordingly to thereby cause a power loss, resulting in deterioration of a power efficiency.
Since, moreover, a distance between the matching circuit 34 and a plasma becomes as large as several wavelengths, an impedance therebetween becomes overwhelmingly greater in comparison with a plasma impedance of the plasma. Consequently, the plasma impedance is not properly reflected in the matching circuit 34, so that it is difficult to appropriately control an ignition of the plasma and a stabilization of the plasma by using the matching circuit 34.